Summary:
We've spent a lot of time hacking around the outputs of hg in jf (a new
tool we use at FB to interact with our code-review system). We've figured out that it
could be all avoided and made cleaner with simple hg extension that dumps all
the data we need in a format that we can easily consume.
Test Plan: see attached test
Reviewers: #fbhgext, ryanmce
Reviewed By: #fbhgext, ryanmce
Subscribers: quark
Differential Revision: https://phab.mercurial-scm.org/D205
